比较jQuery中的两个字符串不起作用

Question

This is my code

function nameIsDuplicate(name){
    objects = $("#content").find('p.itemOldName');
    $(objects).each(function(i, object){
        console.log("*"+($(object).text()).toLowerCase() + "*" + name.toLowerCase()+"*");
        if(($(object).text()).toLowerCase() == name.toLowerCase())
            return true;
    });
    return false;
}

I am building an online file manager system. the name argument is a name provided by the user via a textbox, and the $(object).text() is the name of files and folders in the current directory. These names come via exec("ls") command.

I need to check if the name provided by the user already exists. So I compare the name with every files/folders name. The problem is it doesn't find duplicates. The result of the above code is given in the following image

Answer 1

The return true returns out of the each callback. That has no effect on each (it only cares about return false ) and doesn't do anything to set the return value of nameIsDuplicate .

You want to return false there (no need to keep looking) and set a flag so your nameIsDuplicate can return it:

function nameIsDuplicate(name){
    var duplicate = false;
    objects = $("#content").find('p.itemOldName');
    $(objects).each(function(i, object){
        console.log("*"+($(object).text()).toLowerCase() + "*" + name.toLowerCase()+"*");
        if(($(object).text()).toLowerCase() == name.toLowerCase()) {
            duplicate = true;
            return false; // Stop looping
        }
    });
    return duplicate;
}

However , that function can be a lot simpler using Array.prototype.some :

function nameIsDuplicate(name){
    var objects = $("#content").find('p.itemOldName');
    name = name.toLowerCase();
    return objects.get().some(function(object) {
        return $(object).text().toLowerCase() === name;
    });
}

some calls its callback for each entry in the array. If the callback returns a falsy value, some keeps going; if the callback returns a truthy value, some stops. some 's return value is true if a call to the callback returned a truthy value, false if not.

Answer 2

Your function doesn't return true , because you are in each loop... should be something like this:

function nameIsDuplicate(name){
    var same=0;
    objects = $("#content").find('p.itemOldName');
    $(objects).each(function(i, object){
        console.log("*"+($(object).text()).toLowerCase() + "*" + name.toLowerCase()+"*");
        if(($(object).text()).toLowerCase() == name.toLowerCase()){
            same=1; 
            return false;        
        }
    });
    if(same){
        return true;
    }else{
        return false;
    }
}

We can break the $.each() loop at a particular iteration by making the callback function return false. Returning non-false is the same as a continue statement in a for loop; it will skip immediately to the next iteration.

Other solution:

function nameIsDuplicate(name){
    return $("#content").find('p.itemOldName').filter(function(){return $(this).text().toLowerCase() === name.toLowerCase();}).length;
}